Optocoupler MOC304 dimming control circuit diagram

The dimming control circuit is as shown in the figure. The I/O port of the microcontroller is used to sink current to control the thyristor to achieve switching and dimming control. The photoelectric coupler MOC3041 with internal zero-crossing detection circuit is used as the thyristor driver, which can realize the isolation of strong and weak current at the same time.

Traditional dimming methods use phase-shifted trigger thyristors and control the conduction angle of the thyristor to control the output power. Not only is the synchronous detection circuit complex, but also high-order harmonic interference is generated at the moment the thyristor is turned on, causing distortion of the grid voltage waveform and affecting The normal operation of other electrical equipment and communication systems. In this system, the time ratio between the on and off time of the zero-crossing trigger thyristor is used to adjust the power of the lamp. Since the zero-crossing trigger does not change the waveform of the voltage, it only changes the full wave of the voltage. times and will not cause pollution to the power grid. Therefore, this system adopts the zero-crossing trigger method.

MOC3041 contains an internal zero-crossing detection circuit. When input pin 1 inputs a 15mA current and the voltage between output pins 6 and 4 slightly crosses zero, the internal bidirectional thyristor is turned on, triggering the external thyristor to turn on. When MOC3041 When the input current of the input pin is 0, the internal bidirectional thyristor is turned off, so the external thyristor is also turned off.

ck="window.open(this.src)" alt="Click to see larger image" />